1. Technical Field
The present invention relates to an IP device exchange apparatus and a call connection changing method that transmit or receive voice data to control the connection of IP phones during communication.
2. Background Art
In recent years, with the development of IP techniques, IP device exchange apparatuses, which are called IP-PBX (Private Branch eXchange), have widely spread to the offices. In order to implement the functions of PBX according to the related art, some of the IP-PBXs adopt the following changing method. That is, in order to connect IP phones, an IP-PBX terminates the transmission of RTP packets for forwarding voice data once, and the IP-PBX uses a time-division switch as PCM data to switch the connection of the IP phones. Such an IP device exchange apparatus is called an IP enabled PBX or a PBX with VoIP (Voice over Internet Protocol)-GW (Gateway).
Further, a technique has been proposed in which an interface manager is provided to change the destination of RTP packets and transmit the RTP packets, as the related art for call connection in an IP phone network (for example, see JP-A-2005-191738).
Further, the following apparatuses have been proposed: an IP device exchange apparatus that implements Peer-to-Peer communication between IP phones; and an apparatus that use RTP packets to switch image data as well as voice data. Such a changing apparatus is generally called a softswitch or a call control server.
As such, in the IP-PBX, since the time-division switch can perform changing at an arbitrary timing during communication, it is possible to implement the equivalent complicated and various functions as those in the PBX (legacy PBX) according to the related art. For example, the IP enabled PBX has a ‘steal’ function of changing call connection between IP devices from one IP phone to another IP phone during communication, in response to a request from another IP phone.
However, the IP enabled PBX does not perform Peer-to-Peer communication between IP phones, but the IP enabled PBX system is interposed between the IP phones to control changing therebetween. Therefore, since the IP enabled PBX uses the time-division switch as PCM (pulse-code modulation) data to control changing, the IP enabled PBX repeatedly performs encoding and decoding. As a result, voice quality deteriorates, or apparatuses that can be connected to the IP enabled PBX system are limited to voice apparatuses.
Furthermore, it is necessary that the PBX accepts the connection of various types of IP devices with various functions. In this case, a call control process suitable for the type of IP device is also required.
Meanwhile, since the softswitch according to the related art can implement Peer-to-Peer communication, there is no fear that voice quality will deteriorate. However, it is difficult to change a session at an arbitrary timing during communication according to VoIP. Therefore, the function of the softswitch is considerably deteriorated, as compared the changing function of the PBX.